Just got a set of 13 to 1 pistons From JE.
I shot some photos of the stock piston in one side and the high compression pistons side by side. The ruff surface of the stock piston is because it is a cast piston. That means they poured aluminum into a mold then when it cooled they remove it and machine the ring groves and pin hole. This process makes perfectly good pistons. But not pistons capable of high pressure or temp. When they say forged pistons .That means they pushed the aluminum under pressure into a tube .
This link is long but interesting . How they make pistons. 300 dollars a set with pins and rings seems like a good deal after watching how much work goes into them.
http://youtu.be/bPF7jdPyQaU